With Race Emerging As Fault Line In Senate Race, Census Data Points To Persistently High White Voter Turnout In Mass.

BOSTON New U.S. Census data show non-white voters made up a record share of the Massachusetts electorate last fall.

But over the last 12 years, a WBUR analysis reveals, the white vote has held up stronger in the Bay State than it has nationwide.

The racial cross-currents could play a key role in the U.S. Senate contest pitting U.S. Rep. Edward Markey, a Democrat, against Republican venture capitalist Gabriel Gomez.

A WBUR poll released last week gives Markey a six-point edge on his GOP opponent. And virtually his entire lead is attributable to his sizable advantage with non-white voters — 61 to 9 percent.

“In a close race,” says Jeffrey Berry, a political science professor at Tufts University, “Markey needs to turn out minority voters.”

Last fall’s record minority turnout is no doubt encouraging for the Markey camp; the Census data show that minorities made up 16 percent of the Massachusetts electorate in November.

But that election featured a presidential race and a high-profile clash between U.S. Sen. Scott Brown and his Democratic challenger Elizabeth Warren.

In the November 2010 election — a lower turnout affair more akin to the Markey-Gomez election set for June 25 — the minority share of the electorate was only half as large: 8 percent.

That figure, Census data show, is more in line with the totals in recent elections. And it speaks to the unusual staying power of the white vote in Massachusetts.

Nationwide, the decline of the white vote in recent years has been two-fold. First, whites have shrunk as a share of the voting-age population.

And second, the white voter turnout rate – the percentage of voting-age whites casting ballots – has declined since the 2004 presidential race.

In the Bay State, the white share of the voter-age population has dropped, as it has nationally. But the decline has been partially offset by steady growth in the rate of white voter turnout over the course of the last 12 years.

Berry, the political science professor, attributes the persistently high white voter turnout to the state’s relative affluence. A better-off population is more likely to vote.

“It’s not a matter of Massachusetts virtue,” he says, “it’s a matter of Massachusetts demographics.”

Whatever the explanation, the trend gives Massachusetts Republicans a glimmer of hope – especially in non-presidential year elections where whites make up a particularly large share of the electorate.

That may explain why the Democratic Party and allies like the Service Employees International Union have made a concerted effort over the last couple of election cycles to organize minority voters.

It’s hard to measure the impact of canvassing and phone banking. But between the 2008 and 2012 elections, voter turnout gains in majority-minority cities like Lawrence, Lynn and Springfield outpaced statewide voter turnout growth.

All three municipalities have sizable Latino populations. But the sample sizes in the new Census survey for Latinos, blacks and Asians are too small — at the state level — to draw any definitive conclusions about which group or groups drove the 2012 spike in the non-white share of the electorate.

Whoever was behind the spike, though, it was advantageous for Democrats. And whether Markey can produce anything approaching the demography of the 2012 electorate could prove decisive in his own race.

The Massachusetts data is part of a broader, nationwide survey of 60,000 households. At the national level, the sample sizes for minority groups were large enough to make meaningful findings. And the Census found — among other things — that the black voter turnout rate exceeded the white voter turnout rate for the first time in 2012.